It might just be me...but large isopods like Porcellio laevis or P. dilatus seem to be a better choice than a species of roach, even if not already found in your area (but *I* would frown upon such a practice, your choice). You would end up with next to no plant damage too.
Adding a species of roach, just by their nature, would ensure escapees into the surrounding environment... The niche you are trying to fill is also typically/more easily filled by isopods in nature, with roaches contributing to a lesser extent.